This galaxy is so weird, astronomers aren't even sure what it is

This galaxy is so weird, astronomers aren't even sure what it is

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This amazing-looking galaxy is catalogued NGC 2775 and lies 67 million lightyears from Earth.

In fact, it's so far away – its light has taken so long to reach us – we're looking at the galaxy as it appeared just before the extinction of the dinosaurs.

LEDA 1313424, the Bullseye Galaxy, has 9 visible rings, which are ripples caused by a smaller galaxy firing through its centre. Credit: NASA, ESA, Imad Pasha (Yale), Pieter van Dokkum (Yale)
Credit: NASA, ESA, Imad Pasha (Yale), Pieter van Dokkum (Yale)

But the most interesting thing about this colossal cosmic beast is that astronomers aren't really sure how to define it.

How to classify a galaxy

Galaxies are enormous collections of stars, dust, gas and dark matter, all held together by gravity.

We also know that most major galaxies have a supermassive black hole at their centre.

These supermassive black holes consume any stuff that wanders too close, and as that matter falls inwards, it heats up, causing the centre of the galaxy to glow.

Galaxies come in all shapes and sizes, and the most famous are probably the beautiful spiral galaxies with their twisting, well-defined arms.

But there are also elliptical galaxies, irregular galaxies and many more types besides.

One of the most interesting types of galaxy is a lenticular galaxy, as these galaxies share traits common to both spiral galaxies and elliptical galaxies.

Hubble Space Telescope image of galaxy NGC 2775, from 2020. Credit: ESA/Hubble & NASA, J. Lee and the PHANGS-HST Team. Acknowledgement: Judy Schmidt (Geckzilla)
Hubble Space Telescope image of galaxy NGC 2775, from 2020. Credit: ESA/Hubble & NASA, J. Lee and the PHANGS-HST Team. Acknowledgement: Judy Schmidt (Geckzilla)

Examining NGC 2775

The image of NGC 2775 seen here was captured by the Hubble Space Telescope.

From the image, we can see the galaxy has a huge, homogenous centre that seems devoid of any sort of distinguishable features.

That makes it look like an elliptical galaxy. Ellipticals are thought to be the product of galaxy collisions or mergers, whereby the gravitational churning that occurs when galaxies collide causes them to lose their beautiful, intricate features.

As a result, elliptical galaxies appear more like fuzzy blobs in the sky.

But the outer section of NGC 2775 clearly has structure. It's sporting what look like compacted spiral arms, filled with patches of red and blue that indicate star formation is occurring.

So what type of galaxy is it? Is it a spiral, an elliptical or perhaps even a lenticular?

Hubble Space Telescope image of galaxy NGC 2775, from 2025. Image created using Hubble's 2020 image, with added data captured in infrared light. Credit: ESA/Hubble & NASA, F. Belfiore, J. Lee and the PHANGS-HST Team
Hubble Space Telescope image of galaxy NGC 2775, from 2025. Image created using Hubble's 2020 image, with added data captured in infrared light. Credit: ESA/Hubble & NASA, F. Belfiore, J. Lee and the PHANGS-HST Team

Getting to the bottom of it

The problem with galaxies is that we can only see them from one angle.

Unlike the planets and moons of our Solar System, which we can send spacecraft to orbit and gather views from all aspects, we're stuck viewing galaxies as they appear from Earth.

That's why we see many edge-on galaxies in our Universe: because we've no other way of viewing them.

And that's the issue with trying to understand more about what sort of galaxy NGC 2775 is.

It could be a spiral galaxy, because it clearly has a ring of stars and dust.

Or it could be a lenticular galaxy. Lenticular galaxies may be old spirals that have merged with other galaxies.

Lenticulars might also be galaxies that have run out of the ingredients to form new stars, and have lost their arms.

There is evidence that NGC 2775 has merged with other galaxies in the past, astronomers say.

That's in the form of a huge tail of hydrogen gas stretching 100,000 lightyears around the galaxy (unfortunately not visible in these Hubble images).

The tail could be the remnant of one or more galaxies that were torn apart and devoured by NGC 2775.

Such a merger might help explain why NGC 2775 looks so weird today.

But for now, the jury's still out, and this strange-looking galaxy continues to defy definition.

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